This invention relates to X-ray generator devices and, in particular, to an X-ray generator device comprising a radiation source in the form of a conically tapering front part of a target member to provide X-ray emission with a nearly uniform distribution in a radial plane through the tip of the target member.
Such X-ray generator devices find particular use in certain forms of industrial X-ray examination, in which respect small physical dimensions of the X-ray emitting portion of the generator device are desired as a consequence of the particular character of the object to be examined, for instance when controlling welding. Moreover, a dental X-ray device having a similar design of the X-ray generator device is known from British Patent Specification No. 868,830.
X-ray generators of this type generally include a beam focussing and deflecting system which is directed toward controlling the electron beam emitted from the electron gun as precisely as possible in order to hit the tip of the tapering front part of the target member, thereby providing X-ray emission with a uniform distribution in a radial plane through the point of the cone. Particularly, but not exclusively, as regards X-ray examination of the kind in which the radiation-sensitive detecting member, for instance film, is positioned at a distance from the object to be examined, it is at the same time essential that the physical dimensions of the X-ray source formed by the target member are as small as to appear substantially punctiform. Otherwise, the image formed on the detecting member will actually show a certain blurred contour determined by the physical dimensions of the radiation source and the ratios of distances of the objects from the radiation source and the detecting member, respectively, that will make it difficult to obtain a satisfactory X-ray image.
It is an object of the present invention to provide an X-ray generator device of the above mentioned kind, in which the requirement of hitting the tip of the conical target member as accurately as possible to allow uniform distribution of the radiation in a radial plane is fulfilled by an electron beam having a very small cross-section so that the spatial extent of the radiation source is confined to the top of the target member. It is a further object of the invention to allow the target member to be positioned in an X-ray emitting generator portion of very small physical dimensions which facilitate work on test objects such as pipe welding which make access difficult.